balancing 912 throttles

[awatry]

I tried to get my 69 912's Solexes (split shaft) to draw the same amount of air this weekend with a synch gauge, but the synch screw mechanism pieces, pinned to the butterfly shafts, are all a bit loose, and the rubber pad, which the mechanism bears against as you tighten the balancing screw, is almost gone on one carb and about half gone on the other. So everything's floppy. I assume that they're worn, and that they aren't supposed to be loose, unless there is a separate throttle return spring for the forward throttle shaft so it springs closed on its own, rather than depending on the rear spring, through the linking mechanism. The throttle shafts and butterflies seem OK.

Is there a source of new or good used pieces for these? Anyone have a good procedure to replace them that doesn't bend the throttle shafts? Or anyone have some otherwise lousy carbs, but that have these pieces in decent condition, for sale to cannabilize? I don't want to get into a $700 rebuild program if I can help it. Thanks

Andrew Watry
Berkeley, CA